The objective of this study is to evaluate the relationships between human immune response genes, atopic allergy, the HLA linkage group including HLA, PGM3, GLO and the vigor of the immune response to several antigens. Ten large ragweed sensitive families are being studied. A careful clinical evaluation of atopic allergy will be carried out on each family member. Each subject is being studied regarding the immediate skin test response and quantitation of IgG and IgE antibodies against purified ragweed antigens, HLA antigens, third phosphoglucomutase locus (PGM3), Glyoxalase (GLO), and serum immunoglobulins and red cell antigens. The ragweed antigens used will be standardized and characterized according to purity. The segregation and linkage of the various parameters will be analyzed in order to further our knowledge of the immunogenetics of ragweed atopic disease.